doc: Steps to recover from split-brain

BUG: 1006776
Change-Id: I6f4bffe992758b2889df9ebfe117834dabe5c1cf
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/4216
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>